Dynamic spinal fixation system, method of use, and spinal fixation system attachment portions

ABSTRACT

Spinal fixation systems including a member, a first attachment portion, a second attachment portion, and an intermediate portion. The first attachment portion is attached at a superior end of the member and includes a first opening. The second attachment portion is attached at an inferior end of the member and includes a second opening. The intermediate portion connects the first and second attachment portions. The spinal fixation systems may also include a relief in at least one of the first opening and the second opening. The systems may also include a third attachment portion with a third opening and an intermediate portion with a first and a second elastic mechanism. The first elastic mechanism connects the first and third attachment portions and the second elastic mechanism connects the third and second attachment portions. Surgical methods for inserting the spinal fixation systems in a patient are also disclosed.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.15/337,253 filed Oct. 28, 2016, which is a continuation of U.S.application Ser. No. 14/237,733 filed May 16, 2014, which issued as U.S.Pat. No. 9,510,871 on Dec. 6, 2016 and which is a national stage filingunder section 371 of International Application No. PCT/US2012/049959filed on Aug. 8, 2012 and published in English on Feb. 14, 2013 as WO2013/022944 A1 and claims priority benefit under 35 U.S.C. §119(e) ofU.S. provisional patent application Nos. 61/574,662 and 61/574,636 filedAug. 8, 2011 and U.S. provisional patent application Nos. 61/628,662 and61/628,663 filed Nov. 4, 2011, which are incorporated herein byreference in their entireties.

BACKGROUND OF THE INVENTION

The present disclosure relates generally to a spinal fixation deviceand, in particular, to a dynamic spinal fixation system and method ofuse for stabilizing one or more levels of the cervical spine or lumbarspine as well as to a spinal fixation system including attachmentportions with reliefs. When non-surgical treatments of spinal injuries,diseases, and trauma fail, anterior spinal surgery is often performed toaccess the cervical or lumbar vertebrae or intervertebral discs. Theanterior spinal surgery that is performed may be an anterior cervicaldiscectomy and fusion (“ACDF”). During an ACDF procedure a bone graft orinterbody implant is often used to replace the removed disc and a spinalfixation plate is then attached to adjacent vertebrae to stabilize thespine and foster arthrodesis. Current procedures employ placement of theplate first and the screws to fix that plate to vertebrae second. Mostcommonly, spinal fixation plates are affixed to the vertebrae using bonescrews.

The currently available spinal fixation plates or devices limitvisualization of the vertebrae during placement. In addition, currentlyavailable spinal fixation devices are difficult to place along themidline. The currently available spinal fixation devices also create aninability to align intervening segments for fixation. Finally, thecurrently available spinal fixations devices make it difficult to pullthe vertebrae up into a more lordotic position when significant kyphosisexists.

Accordingly, the present invention contemplates new and improved spinalfixation systems which overcome the above-referenced problems andothers.

SUMMARY OF THE INVENTION

The present invention is directed toward devices and methods for use instabilizing one or more levels of the cervical spine or lumbar spine.

In one aspect of the present invention provided herein, is a dynamicspinal fixation system. The dynamic spinal fixation system includes amember with a superior end and an inferior end. The member includes afirst attachment portion with a first opening at the superior end and asecond attachment portion with a second opening at the inferior end. Anintermediate portion connects the first attachment portion and thesecond attachment portion.

In another embodiment of the present invention provided herein, is adynamic spinal fixation system. The dynamic spinal fixation systemincludes a member with a top end and a bottom end. The member includes afirst attachment portion with a first opening at the top end and asecond attachment portion with a second opening at the bottom end. Anintermediate portion connects the first attachment portion and thesecond attachment portion. At least one of the first and second openingsincludes a relief.

In a further aspect of the present invention provided herein, is asurgical method for fusing a spine. The method includes obtaining adynamic spinal fixation system. The dynamic spinal fixation systemincludes a member with a superior end and an inferior end. The memberincludes a first attachment portion at the inferior end which includes afirst opening with a first relief and a second attachment portion whichincludes a second opening with a second relief. An intermediate portionconnects the first attachment portion and the second attachment portion.A first bone fastener is inserted into a first vertebra of a patient anda second bone fastener is inserted into a second vertebra of thepatient. The first vertebra is superior the second vertebra. The firstrelief is then aligned with the first fastener and the second relief isaligned with the second fastener. The member is moved into alignmentwith the first vertebra and the second vertebra for fixation by slidingthe member to engage the first fastener in the first opening and secondfastener in the second opening. The first fastener is tightened to thefirst vertebra and the second fastener is tightened to the secondvertebra to secure the dynamic spinal fixation system to at least thefirst vertebra and the second vertebra of a patient's spine. The methodis advantageous because it provides a surgeon with the ability to placethe bone fasteners into the spine prior to placement of the dynamicspinal fixation system which assists in placing the system in themidline of the spine while also allowing for ideal fastener placementwith respect to the vertebrae.

These and other objects, features and advantages of this invention willbecome apparent from the following detailed description of the variousaspects of the invention taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention andtogether with the detailed description herein, serve to explain theprinciples of the invention. It is emphasized that, in accordance withthe standard practice in the industry, various features are not drawn toscale. In fact, the dimensions of the various features may bearbitrarily increased or reduced for clarity of discussion. The drawingsare only for purposes of illustrating preferred embodiments and are notto be construed as limiting the invention.

FIG. 1 shows a front view of one embodiment of a two level dynamicspinal fixation system, in accordance with an aspect of the presentinvention;

FIG. 2 shows a front view of one embodiment of a one level dynamicspinal fixation system including reliefs, in accordance with an aspectof the present invention;

FIG. 3 shows a top view of the dynamic spinal fixation system of FIG. 2,in accordance with an aspect of the present invention;

FIG. 4 is a cross-sectional perspective view of the dynamic spinalfixation system shown in FIG. 2 as viewed along section line 4-4 in FIG.2, in accordance with an aspect of the present invention;

FIG. 5 is a side perspective view of the dynamic spinal fixation systemshown in FIG. 4, in accordance with an aspect of the present invention;

FIG. 6 is another embodiment of a one level dynamic spinal fixationsystem from a front view, in accordance with an aspect of the presentinvention;

FIG. 7 shows a front view of yet another embodiment of a one leveldynamic spinal fixation system, in accordance with an aspect of thepresent invention;

FIG. 8 is a perspective view of the dynamic spinal fixation systemembodiment of FIG. 7, in accordance with an aspect of the presentinvention;

FIG. 9 is an additional embodiment of a one level dynamic spinalfixation system from a front view, in accordance with an aspect of thepresent invention;

FIG. 10 shows a further embodiment of a one level dynamic spinalfixation system from a front view, in accordance with an aspect of thepresent invention;

FIG. 11 shows a front view of yet another embodiment of a one leveldynamic spinal fixation system, in accordance with an aspect of thepresent invention;

FIG. 12 is another embodiment of a one level dynamic spinal fixationsystem shown from a front view, in accordance with an aspect of thepresent invention;

FIG. 13 is a perspective view of the dynamic spinal fixation systemembodiment of FIG. 12, in accordance with an aspect of the presentinvention;

FIG. 14 shows another embodiment of a one level dynamic spinal fixationsystem with a hard stop from a front view, in accordance with an aspectof the present invention;

FIG. 15 is a front view of a further embodiment of a one level dynamicspinal fixation system with an alternative hard stop, in accordance withan aspect of the present invention;

FIG. 16 is a front view of yet another embodiment of a one level dynamicspinal fixation system with a further alternative hard stop, inaccordance with an aspect of the present invention;

FIG. 17 shows a front view of an additional embodiment of a one leveldynamic spinal fixation system, in accordance with an aspect of thepresent invention;

FIG. 18 shows another embodiment of a one level dynamic spinal fixationsystem from a front view, in accordance with an aspect of the presentinvention;

FIG. 19 shows a front view of still another embodiment of a one leveldynamic spinal fixation system, in accordance with an aspect of thepresent invention;

FIG. 20 shows a further embodiment of a one level dynamic spinalfixation system from a front view, in accordance with an aspect of thepresent invention;

FIG. 21 is a front view of a two level embodiment of the dynamic spinalfixation system of FIG. 8, in accordance with an aspect of the presentinvention;

FIG. 22 is a front view of a two level embodiment of the dynamic spinalfixation system of FIG. 9, in accordance with an aspect of the presentinvention;

FIG. 23 is a front view of a two level embodiment of the dynamic spinalfixation system of FIG. 10, in accordance with an aspect of the presentinvention;

FIG. 24 is a front view of a two level dynamic spinal fixation systemembodiment that combines the dynamic fixation systems of FIG. 8 and FIG.9, in accordance with an aspect of the present invention;

FIG. 25 is a front view of the one level dynamic spinal fixation systemembodiment of FIG. 8 integrated with an interbody cage, in accordancewith an aspect of the present invention;

FIG. 26 is a front view of another embodiment of a two level dynamicspinal fixation system, in accordance with an aspect of the presentinvention;

FIG. 27 is another embodiment of a two level dynamic spinal fixationsystem with at least one coil spring-like member shown from a frontview, in accordance with an aspect of the present invention;

FIG. 28 is a front view of yet another embodiment of a two level dynamicspinal fixation system with at least two parallel coil spring-likemembers, in accordance with an aspect of the present invention;

FIG. 29 is a further embodiment of a two level dynamic spinal fixationsystem with at least two parallel torsional spring members shown from afront view, in accordance with an aspect of the present invention;

FIG. 30 is a front view of another embodiment of a two level dynamicspinal fixation system with at least two elastic members, in accordancewith an aspect of the present invention;

FIG. 31 is a further embodiment of a two level dynamic spinal fixationsystem with piston members shown from a front view, in accordance withan aspect of the present invention;

FIG. 32 is a front view of a static spinal fixation system embodimentwith attachment portions including openings with reliefs, in accordancewith an aspect of the present invention;

FIG. 33 is a front view of another embodiment of a dynamic spinalfixation system with attachment portions including openings withreliefs; in accordance with an aspect of the present invention;

FIG. 34 is a front view of a further embodiment of a dynamic spinalfixation system with attachment portions including openings withreliefs, in accordance with an aspect of the present invention;

FIG. 35 is a perspective view of the dynamic spinal fixation systemembodiment of FIG. 34, in accordance with an aspect of the presentinvention;

FIG. 36 is a front view of yet another embodiment of a dynamic spinalfixation system with curved attachment portions including openings withreliefs, in accordance with an aspect of the present invention;

FIG. 37 is a perspective view of the dynamic spinal fixation systemembodiment of FIG. 36, in accordance with an aspect of the presentinvention;

FIG. 38 is a front view of another dynamic spinal fixation systemembodiment with attachment portions including openings with off centerreliefs, in accordance with an aspect of the present invention;

FIG. 39 is a front view of a further embodiment of a dynamic spinalfixation system with attachment portions including openings withreliefs, in accordance with an aspect of the present invention;

FIG. 40 is yet another embodiment of a dynamic spinal fixation systemwith attachment portions including openings with reliefs shown from afront view, in accordance with an aspect of the present invention;

FIG. 41 is a front view of an additional embodiment of a dynamic spinalfixation system with attachment portions including openings withreliefs, in accordance with an aspect of the present invention;

FIG. 42 is another embodiment of a dynamic spinal fixation system withattachment portions including openings with reliefs from a front view,in accordance with an aspect of the present invention;

FIG. 43 is a front view of still a further embodiment of a dynamicspinal fixation system with attachment portions including openings withreliefs, in accordance with an aspect of the present invention;

FIG. 44 is a front view of the embodiment dynamic spinal fixation systemof FIG. 41 wherein the openings are curved, in accordance with an aspectof the present invention;

FIG. 45 is a perspective view of the dynamic spinal fixation systemembodiment of FIG. 44, in accordance with an aspect of the presentinvention;

FIG. 46 is an exploded view of another embodiment of a dynamic spinalfixation system with attachment portions including openings with reliefsand two vertebrae with four fasteners secured to the vertebrae, inaccordance with an aspect of the present invention;

FIG. 47 is a front view of the embodiment of FIG. 46 wherein the dynamicspinal fixation system with attachment portions including openings withreliefs is inserted over the fasteners and the arms are in an openposition, in accordance with an aspect of the present invention;

FIG. 48 is a front view of the dynamic spinal fixation system of FIGS.46 and 47 secured to the two vertebrae with closed arms, in accordancewith an aspect of the present invention;

FIG. 49 is a front view of another embodiment dynamic spinal fixationsystem with curved attachment portions secured to two vertebrae, inaccordance with an aspect of the present invention;

FIG. 50 is a front view of yet another embodiment of a dynamic spinalfixation system with curved attachment portions secured to twovertebrae, in accordance with an aspect of the present invention;

FIG. 51 is a front view of the dynamic spinal fixation system of FIGS.34 and 35 with the reliefs of the fixation system mating with twoaligned fasteners secured to two vertebrae, in accordance with an aspectof the present invention;

FIG. 52 is a front view of the dynamic spinal fixation system of FIG. 51after sliding the fixation system along the openings to secure thefasteners, in accordance with an aspect of the present invention;

FIG. 53 is a front view of the dynamic spinal fixation system of FIGS.36 and 37 with the reliefs of the fixation system mating with two offsetfasteners secured to two vertebrae, in accordance with an aspect of thepresent invention;

FIG. 54 is a front view of the dynamic spinal fixation system of FIG. 53after rotation of the fixation system, in accordance with an aspect ofthe present invention;

FIG. 55 is a front view of the dynamic spinal fixation system embodimentof FIGS. 53 and 54 secured to two vertebrae with four fasteners, inaccordance with an aspect of the present invention; and

FIG. 56 depicts one embodiment of a surgical method for implanting adynamic spinal fixation system into a patient's body, in accordance withan aspect of the present invention.

DETAILED DESCRIPTION FOR CARRYING OUT THE INVENTION

In this application, the words proximal, distal, anterior, posterior,medial and lateral are defined by their standard usage for indicating aparticular part or portion of a bone or prosthesis coupled thereto, ordirectional terms of reference, according to the relative disposition ofthe natural bone. For example, “proximal” means the portion of a bone orprosthesis nearest the torso, while “distal” indicates the portion ofthe bone or prosthesis farthest from the torso. As an example ofdirectional usage of the terms, “anterior” refers to a direction towardsthe front side of the body, “posterior” refers to a direction towardsthe back side of the body, “medial” refers to a direction towards themidline of the body and “lateral” refers to a direction towards thesides or away from the midline of the body.

Referring to the drawings, wherein like reference numerals are used toindicate like or analogous components throughout the several views andreferring now to FIG. 1 which depicts a dynamic spinal fixation plate orsystem 10. The dynamic spinal fixation system 10 includes a singlemember 12. The single member 12 is aligned with a first vertebra 14 at asuperior end, a second vertebra 16 at a mid-point, and a third vertebra18 at an inferior end. The system 10 may be secured to the vertebrae 14,16, 18 using bone fasteners, not shown.

The single member 12 may be comprised of a single elastic component witha plurality of straight and curved portions. The single member 12 may bea wire, rod, tube, or other curvilinear spring-like element and may bemade of a metallic, polymer, ceramic, or composite material. The singlemember 12 or elastic component may include a plurality of straightportions 20 and a plurality of curved portions 22 to facilitate fixationof a bone fastener, such as a screw, nail, staple, wire, pin, and thelike, to the vertebrae 14, 16, 18. The plurality of straight portions 20may preferably range from one to fifteen per level and the plurality ofcurved portions 22 may preferably range from one to sixteen per level.More preferably the plurality of straight portions 20 may range from oneto six per level and the plurality of curved portions 22 may range fromone to seven per level. In the depicted embodiment, the single member 12includes thirteen straight portions 20 and twelve curved portions 22.The bone fasteners may be placed through the single member 12 to engagethe vertebrae, specifically the bone fasteners may be placed through anytwo horizontal sections of the single member 12. In alternativeembodiments, the single member 12 may include attachment portions at thepositions where the single member 12 is secured to the vertebrae and theattachment portions may have closed geometries of the types described ingreater detail below.

In addition, the shape of the single member 12 may also facilitatecontrolled deformation in axial compression and in flexion/extensionwhile maintaining a high level of rigidity in lateral bending and in theanterior/posterior direction. The single member 12 of the dynamic spinalfixation system 10 may be comprised of at least one spring-likeelastically deformable element. The spring-like element may becurvilinear in shape and allow for elastic deformation when loaded. Thedeformation of the spring-like element is primarily in the axialdirection allowing for controlled or limited flexion and extension.Further, the single member 12 may be shaped to match the curvature ofthe spine in the sagittal and transverse planes. Alternative shapes thatare advantageous to promote stability or arthrodesis of the spine arealso contemplated.

The single member 12 may have a cross-section that is circular,elliptical, square, rectangular, or another uniform or non-uniformgeometric shape. In addition, the single member 12 may have a uniformgeometry along the sagittal and/or transverse planes. Alternatively, thesingle member 12 may have a non-uniform geometry along the sagittaland/or transverse planes, whereby the single member 12 changes inthickness becoming either thicker or thinner along the sagittal and/ortransverse planes. For example, the single member 12 may be thicker nearthe lateral aspects of the dynamic spinal fixation system 10 and may bethinner near the midline of the dynamic spinal fixation system 10. Asystem 10 with thicker lateral aspects and thinner near the midlinegives the single member 12 a larger cross-section dimension at thelateral sides of the system 10 and a smaller cross-section dimensionnear the midline of the system 10. The single member 12 may also bereinforced with an absorbable biomaterial that is resorbed over time andas the biomaterial is absorbed, the stiffness of the dynamic spinalfixation systems changes.

The system 10 provides for a high proportion of open area betweenplurality of straight and curved portions of the single member 12allowing for easy visualization through the single member 12. The system10 also provides elastic compliance allowing the single member 12 to bepre-compressed or pre-distracted prior to attachment to the vertebrae14, 16, 18. By pre-compressing the single member 12, the system 10 canfacilitate pre-distraction of one or more motion segments of the spinewhen attached to the vertebrae 14, 16, 18. Alternatively, bypre-distracting the single member 12, the system 10 can facilitatepre-compression of one or more motion segments of the spine whenattached to the vertebrae 14, 16, 18.

Referring now to FIGS. 2-5, an alternative embodiment of a dynamicspinal fixation system or plate 550 is shown. The system 550 includes asuperior end 558 and an inferior end 560. A first attachment portion 552is at the superior end 558 of the system 550 and a second attachmentportion 554 is at the inferior end 560 of the system 550. Anintermediate portion 556 connects the first attachment portion 552 andthe second attachment portion 554. The first attachment portion 552 andsecond attachment portion 554 or platform sections may have a generallyclosed geometry such as a circle, ellipse, square, rectangle, or otherclosed geometry to facilitate placement of bone fasteners, such as bonescrews, nails, staples, wires, pins, and the like. The first attachmentportion 552 includes a first opening or slot 562 which is oriented in atransverse direction and further includes a relief 564 or a largeraperture creating a “key hole” slot. Likewise, second attachment portion554 includes a second opening or slot 566 which is oriented in atransverse direction and further includes a relief 568 or largeraperture creating a “key hole” slot. The reliefs 564, 568 are centeredin the first and second openings 562, 566, respectively. In alternativeembodiments, the openings 562, 566 could also include additional reliefsallowing for additional bone fasteners to be inserted into the vertebraebefore placement of the system 550 onto a patient's spine. In otheralternative embodiments, the openings 562, 566 could also be orientedvertically or in any other direction. Multiple openings or tracks 562,566 in each attachment portion 552, 554 may also be included inalternative embodiments.

The reliefs 564, 568 allow the first attachment portion 552 and secondattachment portion 554 to be placed over the bone fastener heads, suchas screw heads, that are already fixed to a vertebral body. The bonefasteners could also be pins, wires, nails, or any other method forfixing system 550 to a bone. The first and second openings 562, 566 aresmaller than the geometry of the head of the bone fastener and thereliefs 564, 568. Thus, the geometry of the first and second openings562, 566, respectively, allows the first and second attachment portions552, 554 to be captured between the bone fastener heads and theunderlying vertebra when the system 550 is slid into position betweenthe head of the bone fasteners and the vertebra. Once the system 550 isin a desired position the surgeon may insert additional bone fastenersto secure the system 550 to the patient's spine

The intermediate portion 556 may be comprised of an elastic mechanismthat includes a plurality of straight portions 570 and a plurality ofcurved portions 572. The straight portions 570 and the curved portions572 of the elastic mechanism provide open areas to allow for easy spinevisualization through the system 550. The elastic mechanism of theintermediate portion 556 may be curvilinear in shape and allow forelastic deformation in any direction when loaded. The deformation of theelastic mechanism or spring-like element is primarily in the axialdirection allowing for flexion and extension. The system 550 is designedto be flexible in the superior/inferior direction and more rigid inlateral bending and torsion. Further, the system 550 may be shaped tomatch the curvature of the spine in the sagittal and transverse planes.As best seen in FIG. 3, the system 550 is curved in the transverse planeto correspond to the shape of the vertebrae. A cross-sectional view ofsystem 550 taken along line 4-4 is shown in FIG. 4 and a side view ofthe system 550 from FIG. 4 is shown in FIG. 5. The system 550 may alsobe curved in the sagittal plane to correspond to the shape of the spine.The intermediate portion 556 may be made of a non-uniform geometricshape and have a uniform or non-uniform cross-sectional geometry.

Referring now to FIG. 6, another embodiment dynamic spinal fixationsystem or plate 100 is shown. The system 100 includes a first attachmentportion 102, a second attachment portion 104, and an intermediateportion 106 connecting the first attachment portion 102 and the secondattachment portion 104. The first attachment portion or platform 102 isat a superior end 108 of the system 100 and the second attachmentportion or platform 104 is at an inferior end 110. The first attachmentportion 102 and second attachment portion 104 may be rigid sections foraffixing the system 100 to the vertebrae. The intermediate portion 106may be comprised of an elastic mechanism that has a less rigid elasticmember with spring-like section for fostering controlled deformation.

The first attachment portion 102 includes a first opening 112 and thesecond attachment portion 104 includes a second opening 114. Theopenings 112 and 114 may be used to secure the system 100 to at leasttwo adjacent vertebrae using bone fasteners. The uniform openings 112and 114 allow for bone fastener placement anywhere along the openings112 and 114. Alternatively, the first and second attachment portions 102and 104 may include solid sections with at least one aperture throughthe attachment portions 102 and 104 to allow for placement of bonefasteners through the attachment portions 102 and 104 at pre-designatedlocations.

The intermediate portion 106 may be comprised of an elastic mechanismthat includes a plurality of straight portions 116 and a plurality ofcurved portions 118. The straight portions 116 and the curved portions118 of the elastic mechanism provide open areas to allow for easy spinevisualization through the system 100. The elastic mechanism of theintermediate portion 106 may be curvilinear in shape and allow forelastic deformation in any direction when loaded. The deformation of theelastic mechanism or spring-like element is primarily in the axialdirection allowing for flexion and extension. The system 100 is designedto be flexible in the superior/inferior direction and more rigid inlateral bending and torsion. Further, the system 100 may be shaped tomatch the curvature of the spine in the sagittal and transverse planes.

As seen in FIGS. 7 and 8, the dynamic spinal fixation system or plate120 includes a first attachment portion 102, a second attachment portion104, an intermediate portion 106, and at least one support strut 122.The first attachment portion 102 and second attachment portion 104 areof the type described above with reference to FIG. 6. The support struts122 may be lateral to the midline to enhance the rigidity of the elasticmechanism, in particular in bending and torsion, while still allowingthe system 120 to deform elastically. In alternative embodiments thesupport struts 122 may be along the midline of the system 120. Thesupport struts 122 provide at least one additional support between thestraight portions 116 of the intermediate portion 106 and may begenerally parallel to the curved portions 118. In alternativeembodiments, the struts 122 may have a radius of curvature smaller thanthe radius of curvature of the curved portions 118. The support struts122 also create an opening 124 between the curved portions 118 and thesupport struts 122. In the depicted embodiment there are four supportstruts 122. Additional support struts may also be added generally inparallel with the support struts 122 to provide additional rigidity tothe intermediate portion 106.

Another dynamic spinal fixation system 140 or plate is shown in FIG. 9.The system 140 includes first attachment portion 102, second attachmentportion 104, and intermediate portion 142. The first attachment portion102 and second attachment portion 104 are of the type described abovewith reference to FIGS. 6-8. The intermediate portion 142 may includetwo or more separate portions. In the depicted embodiment of system 140the intermediate portion 142 includes a first intermediate side 144parallel to a second intermediate side 146. The first intermediate side144 is a mirror image of the second intermediate side 146. Theintermediate portion 142 connects the first attachment portion 102 andthe second attachment portion 104. The first intermediate side 144 mateswith the inferior side of the first attachment portion 102 on a firstlateral end 148 and with the superior side of the second attachmentportion 104 on a first lateral end 152. The second intermediate side 146mates with the inferior side of the first attachment portion 102 on asecond lateral end 150 and with the superior side of the secondattachment portion 104 on a second lateral end 154. The intermediateportion 142 is less rigid than the first and second attachment portions102, 104 to allow for controlled elastic deformation. The spring-likeelastic first intermediate side 144 and second intermediate side 146enhance the rigidity of the two or more sides 144, 164, in particular inbending and torsion, while still allowing the system to deformelastically.

Referring now to FIG. 10, a dynamic spinal fixation system 160 is shown.The dynamic spinal fixation system 160 includes first attachment portion102, second attachment portion 104, and intermediate portion 162. Thefirst attachment portion 102 and second attachment portion 104 are ofthe type described above with reference to FIG. 8. The intermediateportion 162 may include two or more separate sides. In the depictedembodiment of system 160, the intermediate portion 162 includes a firstintermediate side 164 parallel to a second intermediate side 166. Thefirst intermediate side 164 is a mirror image of the second intermediateside 166. The intermediate portion 162 connects the first attachmentside 102 and the second attachment side 104. The first intermediate side164 mates with an inferior side of the first attachment side 102 at afirst medial position 168 and with the superior side of the secondattachment portion 104 at a first medial position 172. The secondintermediate side 166 mates with the inferior side of the firstattachment portion 102 at a second medial position 170 and with thesuperior side of the second attachment portion 104 at a second medialposition 174. The intermediate portion 162 is less rigid than the firstand second attachment portions 102, 104 to allow for controlled elasticdeformation. The system 160 allows for elastic motion primarily in theaxial (flexion/extension) direction while the amount of motion inlateral bending and torsion is dictated by the configuration of thespring-like elements.

Referring now to FIG. 11, an alternative embodiment of a dynamic spinalfixation system or plate 50 is shown. The system 50 includes a member 52with a superior end 60 and an inferior end 62. A first attachmentportion 54 is at the superior end 60 of the member 52 and a secondattachment portion 56 is at the inferior end 62 of the member 52. Anintermediate portion 58 connects the first attachment portion 54 and thesecond attachment portion 56. The first attachment portion 54 and secondattachment portion 56 or platform sections may have a generally closedgeometry such as a circle, ellipse, square, rectangle, or other closedgeometry to facilitate placement of bone fasteners, such as bone screws,nails, staples, wires, pins, and the like. The first attachment portion54 includes a first opening 64 and the second attachment portion 56includes a second opening 66. The openings 64 and 66 may be used tosecure the system 50 to at least two adjacent vertebrae using bonefasteners. The openings 64 and 66 allow for bone fastener placementanywhere along the openings 64 and 66 because there are nopre-designated locations for the bone fasteners. Alternatively, thefirst and second attachment portions 54 and 56 may include solidsections with at least one aperture through the attachment portions 54and 56 to allow for placement of bone fasteners through the attachmentportions 54 and 56 at pre-designated locations. The intermediate portion58 includes at least one closed member 68. The closed member 68 may beelastic. In the depicted embodiment there are four closed members 68. Inthe preferred embodiments the closed members 68 may range from one toten. The closed elastic members 68 may have an elliptical, circular,rectangular, square, or any other closed shape. The closed elasticmembers 68 may also be made of a non-uniform geometric shape and have auniform or non-uniform cross-sectional geometry. The member 52 may becurved in the transverse plane to correspond to the shape of thevertebrae. The member 52 may also be curved in the sagittal plane tocorrespond to the shape of the spine.

Another dynamic spinal fixation system 180 is depicted in FIGS. 12 and13. The dynamic spinal fixation system 180 includes first attachmentportion 102, second attachment portion 104, and an intermediate portion182. The intermediate portion 182 includes a first intermediate side 184and a second intermediate side 186. The first attachment portion 102,second attachment portion 104, and the first intermediate side 184 areof the type described above with reference to FIG. 6. The secondintermediate side 186 is a mirror image of the first intermediate side184. The first intermediate side 184 includes a first plurality ofcurved portions 188 and a first plurality of straight portions 190. Thesecond intermediate side 186 includes a second plurality of curvedportions 192 and a second plurality of straight portions 194. The firstintermediate side 184 is connected to the first attachment portion 102and the second attachment portion 104 on the anterior aspect and thesecond intermediate side 186 is connected to the first attachmentportion 102 and the second attachment portion 104 on the posterioraspect. The first intermediate side 184 overlaps with the secondintermediate side 186. The first plurality of straight portions 190 andthe second plurality of straight portions 194 are aligned while thefirst plurality of curved portions 188 and the second plurality ofcurved portions 192 are opposite each other. In alternative embodiments,the plurality of curved portions could be aligned and the plurality ofstraight portions could be offset. The intermediate portion 182 enhancesrigidity by adding a second intermediate side 186 to the firstintermediate side 184. However, even with the enhanced rigidity of theintermediate portion 182, the system 180 is able to deform elastically.Additional intermediate portions could also be added to further enhancerigidity of the system 180 while still allowing the system 180 to deformelastically. The first intermediate side 184 and the second intermediateside 186 may have uniform or non-uniform cross-sectional geometry.

Referring now to FIG. 14, another embodiment dynamic spinal fixationsystem 200 is shown. The system 200 is of the type described above withreference to FIG. 6 including a first attachment portion 102, a secondattachment portion 104, and an intermediate portion 106. The system 200further includes at least one hard stop 202 attached to the intermediateportion 106. In the depicted embodiment there are four hard stops 202and the hard stops 202 comprise arced members positioned between twoadjacent straight portions 116. The hard stops 202 may also be placedbetween two adjacent curved portions 118. The hard stops 202 limit theamount of deformation of the intermediate portion 106 when the system200 is in compression. When the system 200 experiences compressiveloading or bending, the intermediate member 106 deforms until the hardstops 202 are engaged on the adjacent straight portions 116. When thehard stops 202 contact the straight portions 116 deformation is limited.

Depicted in FIG. 15, is another dynamic spinal fixation system 220including first attachment portion 102, second attachment portion 104,and intermediate portion 106 as described above with reference to FIG.6, and further comprising at least one alternative hard stop 222. Thehard stop 222 is attached to the intermediate portion 106 and has agenerally domed shape. In the depicted embodiment, there are four hardstops 222 located between two adjacent straight portions 116. Althoughnot shown, it is also contemplated that the hard stops 222 may be placedbetween two curved portions 118. The hard stops 222 also limit theamount of deformation in the intermediate portion 106 during compressionof the system 220. During compression of the system 220, theintermediate portion 106 is squeezed together until at least onestraight portion 116 makes contact with an adjacent a hard stop 222.

FIG. 16 illustrates another embodiment dynamic spinal fixation system240 including first attachment portion 102, second attachment portion104, and intermediate portion 106 as described above with reference toFIG. 6, and further comprising at least one alternative hard stop 242.The hard stops 242 are redundant hard stops. In the depicted embodiment,there are four hard stops 242. The hard stop 242 includes a first member244 and a second member 246. The first member 244 is arced from a firstend 248 to a second end 250. The second member 246 is also arced from afirst end 252 to a second end 254. The first end 248 of the first member244 and the first end 252 of the second member 246 are attached toadjacent straight portions 116. While the second end 250 of the firstmember 244 and the second end 254 of the second member 246 are arcedtowards each other in order for second end 250 to overlap with secondend 254.

Under compressive loading, tensile loading, or bending the intermediateportion 106 deforms until the hard stops 242 are engaged on the matingfeatures, which include the first member 244, the second member 246, andthe second ends 250, 254 of the first member 244 and second member 246,respectively. The amount of deformation of the intermediate portion 106is limited in compression when the first members 244 and second members246 of the hard stops 242 contact an adjacent straight portion 116. Inaddition the amount of deformation of the intermediate portion 106 isalso limited in tension when the second end 250 of the first member 244and the second end 254 of the second member 246 engage each other.

The intermediate members 58, 106,142, 162, 182, and 556, of FIGS. 2-16may be reinforced with an absorbable biomaterial that is resorbed overtime and as the biomaterial is absorbed, the stiffness of the dynamicspinal fixation systems changes.

Referring now to FIG. 17, yet another embodiment dynamic spinal fixationsystem 260 is shown. The system 260 including first attachment portion102 and second attachment portion 104 as described above with referenceto FIG. 6, and further includes an intermediate portion 262. Theintermediate portion 262 connects the first attachment portion 102 andthe second attachment portion 104 and includes at least one curve 264.In the depicted embodiment the at least one curve 264 arcs in agenerally medial direction relative to the system 260.

Another embodiment dynamic spinal fixation system 280 is illustrated inFIG. 18. The system 280 including first attachment portion 102 andsecond attachment portion 104 as described above with reference to FIG.6, and further includes an intermediate portion 282. The intermediateportion 282 connects the first attachment portion 102 and the secondattachment portion 104. The intermediate portion 282 is a more complexportion and includes multiple curved sections 284 and multiple straightsections 286. In the depicted embodiment the intermediate portion 282 isnarrower in width than the first and second attachment portions 102, 104and is located in a generally medial position.

Depicted in FIG. 19 is still another embodiment dynamic spinal fixationsystem 300. The system 300 including first attachment portion 102 andsecond attachment portion 104 as described above with reference to FIG.6, and further includes an intermediate portion 302. The intermediateportion 302 connects the first attachment portion 102 and the secondattachment portion 104. The intermediate portion 302 includes at leastone wide curve 304 per level. In the depicted embodiment theintermediate portion 302 includes two wide curves 304.

Referring now to FIG. 20 another dynamic spinal fixation system 320 isshown. The system 320 includes first attachment portion 102 and secondattachment portion 104 as described above with reference to FIG. 6, andfurther includes an intermediate portion 322. The intermediate portion322 connects the first attachment portion 102 and the second attachmentportion 104. The intermediate portion 322 includes a solid or closedelastic member or element 324. The solid member 324 may be of any shapethat deforms elastically when loaded.

The intermediate portions 262, 282, 302, and 322 of FIGS. 17-20 may bemade of a metal, polymer, ceramic, or composite material. Further theintermediate portions 262, 282, 302, and 322 of FIGS. 17-20, may bereinforced with an absorbable biomaterial that is resorbed over time andas the biomaterial is absorbed, the stiffness of the dynamic spinalfixation systems changes.

The dynamic spinal fixation systems of FIGS. 2-20 each illustrate a onelevel system. Each of the systems of FIGS. 2-20 can be modified toinclude additional attachment portions and either additional orelongated intermediate portions for engaging more than two adjacentvertebrae. For example and as seen in FIGS. 21-24, the dynamic spinalfixation system 340 is a two level system for the spine. The system 340includes a first attachment portion 102 and a second attachment portion104 as described above with reference to FIG. 8, and further includes anintermediate portion 342. The intermediate portion 342 includes a firstintermediate member 344, a third attachment portion 346, and a secondintermediate member 348. The first intermediate member 344 and secondintermediate member 348 may be reinforced with an absorbable biomaterialthat is resorbed over time and as the biomaterial is absorbed, thestiffness of the dynamic spinal fixation systems changes. The thirdattachment portion 346 may be rigid for affixing the system 340 to avertebra. The third attachment portion 346 includes a third opening 350which may be used to secure the system 340 to a vertebra using at leastone bone fastener. The third opening 350 is uniform and therefore allowsfor placement of bone fasteners at any point along the third opening350. The first, second, and third openings 112, 114, and 350,respectively, may include a ridge or lip for the bone fasteners to matewith when inserted into the patient's vertebrae to maintain a lowprofile of the first, second, and third attachment portions 102, 104,and 346, respectively. The low profile will prevent the bone fastenersfrom protruding above the first, second, and third attachment portions102, 104, and 346, respectively, and agitating the patient's tissue.Alternatively, the attachment portions 102, 104, and 346 may includesolid sections with at least one aperture through the platform to allowfor placement of bone fasteners through the attachment portions 102,104, and 346 at pre-designated locations.

Referring now to FIG. 21, the first intermediate member 344 and thesecond intermediate member 348 are of the type illustrated in FIG. 6 anddescribed with reference to intermediate portion 106. The firstintermediate member 344 and the second intermediate member 348 may eachbe comprised of a single elastic component including a plurality ofstraight portions 352 and a plurality of curved portions 354. Thestraight portions 352 and the curved portions 354 provide open areasthat allow for easy visualization through the system 340 to a patient'sspine. The first intermediate member 344 and the second intermediatemember 348 may be curvilinear in shape and allow for elastic deformationin any direction when loaded. Further, the system 340 may be shaped tomatch the curvature of the spine in the sagittal and transverse planes.

Referring now to FIG. 22, the dynamic spinal fixation system 340includes an alternative first intermediate member 344 and secondintermediate member 348 of the types illustrated in FIG. 7 and describedabove with reference to intermediate portion 106 including at least onesupport strut 122. The first intermediate member 344 and the secondintermediate member 348 may each be comprised of a single elasticcomponent including a plurality of straight portions 352 and a pluralityof curved portions 354. The support struts 122 may be lateral to themidline of the system 340 enhance the rigidity of the first intermediatemember 344 and the second intermediate member 348, in particular inbending and torsion, while still allowing elastic deformation. Thesupport struts 122 provide at least one additional rod between thestraight portions 352 of the first intermediate member 344 and thesecond intermediate member 348 and are generally parallel to the curvedportions 354. Alternatively, the struts 122 may have a radius ofcurvature smaller than the radius of curvature of the curved portions118. The support struts 122 also create an opening 124 between thecurved portions 354 and the support struts 122. In the depictedembodiment there are four support struts 122 for each of the firstintermediate member 344 and the second intermediate member 348.

Referring now to FIG. 23, the dynamic spinal fixation system 340includes yet another alternative first intermediate member 344 and thesecond intermediate member 348. The first intermediate member 344 andsecond intermediate member 348 are of the type illustrated in FIG. 9 anddescribed with reference to intermediate portion 142. The firstintermediate member 344 and second intermediate member 348 each includea first portion 144 parallel to a second portion 146. The first portion144 is a mirror image of the second portion 146. The first intermediatemember 344 connects the first attachment portion 102 and the thirdattachment portion 346. The first portion 144 mates with the inferiorside of the first attachment portion 102 on a first lateral end 148 andwith the superior side of the third attachment portion 346 on a firstlateral end 360. The second portion 146 mates with the inferior side ofthe first attachment portion 102 on a second lateral end 150 and withthe superior side of the third attachment portion 346 on a secondlateral end 362. The second intermediate member 348 connects the thirdattachment portion 346 and the second attachment portion 104. The firstportion 144 mates with the inferior side of the third attachment portion346 on a first lateral end 364 and with the superior side of the secondattachment portion 104 on a first lateral end 152. The second portion146 mates with the inferior side of the third attachment portion 346 ona second lateral end 366 and with the superior side of the secondattachment portion 104 on a second lateral end 154.

The intermediate portions 344 and 348 are less rigid than the first,second, and third attachment portions 102, 104, 346, respectively, toallow for controlled elastic deformation. The spring-like elastic firstportions 144 and second portions 146 enhance the rigidity of the two ormore intermediate portions 344 and 348, in particular in bending andtorsion, while still allowing the intermediate portion to deformelastically.

Referring now to FIG. 24, the dynamic spinal fixation system 340includes a first intermediate member 344 that is different than thesecond intermediate member 348. In the depicted embodiment the firstintermediate member 344 is of the type illustrated in FIG. 6 anddescribed with reference to intermediate portion 106 and the secondintermediate member 348 is of the type illustrated in FIG. 7 anddescribed with reference to intermediate portion 106 and including atleast one support strut 122. The hybrid two level construct ofintermediate portion 342 includes a first intermediate member 344 thatis a more elastic member and a second intermediate member 348 that is amore rigid member. Alternative multi-level dynamic spinal fixationsystems may include various combinations of the intermediate portions ofFIGS. 2-20. Each of the intermediate portions of FIGS. 2-20 may havedifferent medial and lateral stiffness. For example, the medialstiffness may be higher than the lateral stiffness alternatively themedial stiffness may be lower than the lateral stiffness. These hybridmulti-level systems may be used to augment the stiffness of spinallevels adjacent to a single (central) level anterior cervical discectomyand fusion (“ACDF”).

Although only single and double level dynamic spinal fixation systemshave been shown and described, additional levels may be added to thesystems as needed to stabilize a patient spine, creating systems withthree levels or more. In addition, the multi-level systems may includemore than three alternating attachment portions and intermediateportions for longer ACDFs.

Illustrated in FIG. 25 is another embodiment dynamic spinal fixationsystem 380 of the type described above with reference to FIG. 6 andfurther including an interbody fusion cage device 382. The system 380includes a first attachment portion 102, a second attachment portion104, and an intermediate portion 106 of the type described above withreference to FIG. 6. The device 382 includes a hollow member 384 with acavity 386. A bone graft may be inserted into the cavity 386 to allowfor fusion to occur between two adjacent vertebrae. The interbody fusioncage device 382 is integrated into the dynamic spinal fixation system380. The device 382 and system 380 may be pre-assembled prior to surgeryor may be assembled during surgery. During surgery, the device 382 isplaced into the disc space of the spine. Then the system 380 is alignedwith a first vertebra 388 and a second vertebra 390 and may be affixedto the vertebrae using bone fasteners as described above with referenceto FIG. 6. The dynamic spinal fixation systems of FIGS. 2-25 may becomprised of a metallic material, or alternatively of an elastic,hyperelastic, or deformable polymer, ceramic, or composite material.

An alternative dynamic spinal fixation system 400 is depicted in FIG.26. The system 400 includes a first attachment portion 402, a secondattachment portion 404, a third attachment portion 406, a firstintermediate portion 408, and a second intermediate portion 410. Thefirst intermediate portion 408 connects the first attachment portion 402and the second attachment portion 404. The second intermediate portion410 connects the second attachment portion 404 and the third attachmentportion 406. The first attachment portion 402, second attachment portion404, and third attachment portion 406 each include two bone fasteneropenings 412 for using to secure the system 400 to a patient'svertebrae. The first intermediate portion 408 includes a first elasticelement 414, which may be a continuous curved torsional spring-likeelement, and four arms 416 connecting the first elastic element 414 andthe fastener openings 412 of the first and second attachment portions402 and 404, respectively. The second intermediate portion 410 includesa second elastic element 418, which may also be a continuous curvedtorsional spring-like element, and four arms 420 connecting the secondelastic element 418 and the fastener openings 412 of the second andthird attachment portions 404 and 406, respectively. The firstintermediate portion 408 and second intermediate portion 410 may bereinforced with an absorbable biomaterial that is resorbed over time andas the biomaterial is absorbed, the stiffness of the dynamic spinalfixation systems changes.

The system 400 may be attached to a patient's spine by securing fasteneropenings 412 of the first attachment portion 402 to a first vertebra422, fastener openings 412 of the second attachment portion 404 to asecond vertebra 424, and fastener openings 412 of the third attachmentportion 406 to a third vertebra 426. When loaded the system 400 deformselastically by rotation around the torsion spring elements or the firstintermediate portion 408 and second intermediate portion 410. The system400 can be pre-compressed or pre-extended prior to attachment to apatient's first, second, and third vertebrae 422, 424, and 426,respectively, to facilitate distraction or compression, respectively.

Referring now to FIGS. 27-31, another embodiment dynamic spinal fixationsystem 450 is illustrated. The system 450 includes a first attachmentportion 452, a second attachment portion 454, a third attachment portion456, a first intermediate portion 458, and a second intermediate portion460. The first attachment portion 452, second attachment portion 454,and third attachment portion 456 are more rigid for affixing the system450 to a patient's vertebrae. The first attachment portion 452, secondattachment portion 454, and third attachment portion 456 include a firstopening 462, a second opening 464, and a third opening 466,respectively. The first opening 462 may be used to secure the system 100to a first vertebra 468 using bone fasteners. The second opening 464 maybe used to secure the system 100 to a first vertebra 470 using bonefasteners. The third opening 466 may be used to secure the system 100 toa first vertebra 472 using bone fasteners.

The first intermediate portion 458 and a second intermediate portion460, or spring-like elastic sections, are less rigid than the attachmentportions 452, 454, 456 for fostering controlled elastic deformation. Thefirst intermediate portion 458 connects the first attachment portion 452and second attachment portion 454. The second intermediate portion 460connects the second attachment portion 454 and third attachment portion456. As best seen in FIG. 27, the first intermediate portion 458 andsecond intermediate portion 460 may each include a single elasticelement 474 with a plurality of coils. Alternatively and as depicted inFIG. 28, the first intermediate portion 458 and second intermediateportion 460 may each include a first elastic element 476 with aplurality of coils and a second elastic element 478 with a plurality ofcoils. The first elastic element 476 is parallel with the second elasticelement 478 and both are comprised of elastic, metallic, spring-likecomponents with uniform or non-uniform cross-sectional geometry.Additional parallel elastic elements could also be added to theintermediate portions 458, 460. The system 450 illustrated in FIG. 28may also be monolithic and comprised of only a single component.

FIG. 29 depicts another embodiment of first intermediate portion 458 andsecond intermediate portion 460, wherein the first and secondintermediate portions 458 and 460 respectively, each include a firstelastic element 480 with a single coil and a second elastic element 482with a single coil. The first elastic element 480 is parallel to thesecond elastic element 482. The first element 480 and second element 482may be elastic torsional spring-like elements. Additional parallelelastic elements may be added in parallel to first and second elasticelements 480, 482.

Illustrated in FIG. 30 is another embodiment of first intermediateportion 458 and second intermediate portion 460. The first intermediateportion 458 includes a first elastic element 484 parallel to a secondelastic element 486. The first element 484 and second element 486 areelastic leaf spring-like elements.

Referring now to FIG. 31, yet another embodiment of first intermediateportion 458 and second intermediate portion 460 is shown. The firstintermediate portion 458 and second intermediate portion 460 include atleast one piston element 490 in series with an elastic element 492. Theelastic element 492 being in series with the piston element 490 offersresistance to deformation. When the system 450 deforms under a load itis guided by the piston element 490 which is rigid in all directionsother than vertical. The system 450 may also be compressed or extendedprior to being secured to a patient's spine to allow for pre-distractionor pre-loading of the patient's spine.

The system 450 in FIGS. 27-31 can be pre-compressed or pre-extendedprior to attachment to a patient's first, second, and third vertebrae468, 470, and 472, respectively, to facilitate distraction orcompression, respectively. In addition, each configuration of theintermediate portions of system 450 allows for elastic motion primarilyin the axial (flexion/extension) direction while the amount of motion inlateral bending and torsion is dictated by the configuration of theintermediate portions of the systems 450. Further, additional elasticelements may be added in parallel to the intermediate portions of thesystems 450 in FIGS. 28-30 to enhance the rigidity of the system 450, inparticular in bending and torsion, while still allowing the system 450to deform elastically. The intermediate portions 458, 460 of FIGS. 27-31can have different geometries including but not limited to simple andslightly curved or complex and multiply curved, with narrow curves orwide curves, with one, two or more curves per level. The intermediateportions 458, 460 can also be solid or closed geometries that areelastically deformable such as metals, polymers, or composites. Thefirst intermediate portion 458 and second intermediate portion 460 ofFIGS. 27-31 may be reinforced with an absorbable biomaterial that isresorbed over time and as the biomaterial is absorbed, the stiffness ofthe dynamic spinal fixation systems changes.

In addition, as each of the dynamic spinal fixation systems of FIGS.26-31 have been described with reference to three sections for engagingthree adjacent vertebrae and two intermediate deformable portions orcompliant sections for a two-level anterior cervical discectomy andfusion (“ACDF”), it should be understood that each of the systems inFIGS. 26-31 can be modified for a single-level ACDF. A single-level ACDFwould only include two sections for engaging two adjacent vertebrae andone intermediate portion or elastic section. Similarly, it should alsobe understood that each of the systems in FIGS. 26-31 can be modified toinclude more than three alternating attachment sections and intermediatesections for longer ACDF's, which may be more than two-levels.

FIGS. 32-36 show spinal fixation systems that allow the bone fasteners,for example, screws, to be secured to the vertebrae before the systemsare placed onto the spine. The systems generally contain at least twoattachment portions or rigid platform-like sections which are used tosecure the systems to a patient's vertebrae. The attachment portions aregenerally more rigid than the rest of the system to facilitate bonefastener fixation to the bony vertebral bodies by allowing bonefasteners, such as screws, nails, staples, wires, pins, and the like, topass through the systems at the attachment portion or portions.

FIGS. 32 and 33 illustrate a monolithic implant 500 and amulti-component implant 510, respectively. The implant 500 is a staticspinal fixation implant and the implant 510 is a dynamic implant. Theimplants 500, 510 each include a first attachment portion 520 includingan opening 522 with a relief 524, a second attachment portion 526including an opening 528 with a relief 530, and an intermediate portion518. The first and second attachment portions 520, 526 allow for asurgeon to insert the bone fasteners into the vertebrae first, thereby,providing a complete view of the patient's spine. Then the surgeon mayinsert the implants 500, 510 by placing them over the bone fasteners atthe reliefs 524, 530 and sliding the bone fasteners into position withinthe openings 522, 528. Once the bone fasteners are in place along theopenings 522, 528, additional bone fasteners may be inserted to securethe implants 500, 510 to the vertebrae. The intermediate portions 518may be reinforced with an absorbable biomaterial that is resorbed overtime and as the biomaterial is absorbed, the stiffness of the dynamicspinal fixation systems changes. Referring now to FIG. 33, themulti-component implant 510 allows for some adjustment in length of theintermediate portion 518 along the long axis of the implant 510.

Referring now to FIGS. 34 and 35, another dynamic spinal fixation systemor plate 550 embodiment is shown. The system 550 includes a firstattachment portion 552, a second attachment portion 554, and anintermediate portion 556 that connects the first attachment portion 552and second attachment portion 554. The intermediate portion 556 may beof the type described above with reference to FIG. 2 and include anelastic mechanism composed of a plurality of straight portions 570 and aplurality of curved portions 572. The first attachment portion 552 is ata superior end 558 of the system 550 and the second attachment portion554 is at an inferior end 560. The first attachment portion 552 includesa first opening or slot 562 which is oriented in a transverse directionand further includes a relief 564 or a larger aperture creating a “keyhole” slot. Likewise, second attachment portion 554 includes a secondopening or slot 566 which is oriented in a transverse direction andfurther includes a relief 568 or larger aperture creating a “key hole”slot. The reliefs 564, 568 are centered in the first and second openings562, 566, respectively. In alternative embodiments, the openings 562,566 could also include additional reliefs allowing for additional bonefasteners to be inserted into the vertebrae before placement of thesystem 550 onto a patient's spine. In other alternative embodiments, theopenings 562, 566 could also be oriented vertically or in any otherdirection. Multiple openings or tracks 562, 566 in each attachmentportion 552, 554 may also be included in alternative embodiments.

The reliefs 564, 568 allow the first attachment portion 552 and secondattachment portion 554 to be placed over the bone fastener heads, suchas screw heads, that are already fixed to a vertebral body. The bonefasteners could also be pins, wires, nails, or any other method forfixing system 550 to a bone. The first and second openings 562, 566 aresmaller than the geometry of the head of the bone fastener and thereliefs 564, 568. Thus, the geometry of the first and second openings562, 566, respectively, allows the first and second attachment portions552, 554 to be captured between the bone fastener heads and theunderlying vertebra when the system 550 is slid into position betweenthe head of the bone fasteners and the vertebra. Once the system 550 isin a desired position the surgeon may insert additional bone fastenersto secure the system 550 to the patient's spine.

An alternative embodiment dynamic spinal fixation system 600 is depictedin FIGS. 36 and 37. The system 600 includes a first attachment portion602, a second attachment portion 604, and an intermediate portion 606that connects the first attachment portion 602 and second attachmentportion 604. The intermediate portion 606 may be of the type describedabove with reference to FIG. 2 and include a single elastic mechanismthat includes a plurality of straight portions 620 and a plurality ofcurved portions 622. The first attachment portion 602 is at a superiorend 608 of the system 600 and the second attachment portion 604 is at aninferior end 610. The first attachment portion 602 includes a firstopening or slot 612 which is curved and further includes a relief or asingle larger aperture 614. Likewise, second attachment portion 604includes a second opening or slot 616 which is curved and furtherincludes a relief or single larger aperture 618. The openings 612, 616could also include additional reliefs allowing for additional bonefasteners to be inserted into the vertebrae before placement of thesystem 600 onto a patient's spine. The openings 612, 616 of system 600are concave slots that may be used to compress the intermediate portion606 as the system 600 is slid transversely under the already-placed oneor more screws or fasteners. Alternatively, the concave slots ofopenings 612, 616 may be used to distract the intermediate portion 606or to maintain the same distance between the vertebrae based on theposition the fasteners are inserted into the vertebrae. The slots 624could also be convex allowing the motion segment to be distracted. Thesystem 600 may be inserted onto the spine as described above withreference to FIGS. 34 and 35, however rather than sliding the systeminto position, the surgeon would rotate the system 600 into positionbetween the head of the bone fasteners and the vertebra.

The dynamic spinal fixation systems of FIGS. 38-39 depict embodimentssimilar to those described above with reference to FIGS. 34-35, butwherein the systems include alternative relief positions. The reliefsmay be located superiorly or inferiorly to the openings of theattachment portions to facilitate compression or distraction of thedynamic spinal fixation systems.

Referring now to FIG. 38, the dynamic spinal fixation system 650includes first attachment portion 652, second attachment portion 654,and intermediate portion 556 which connects first attachment portion 652and second attachment portion 654. The first attachment portion 652 isat a superior end 656 of the system 650 and the second attachmentportion 654 is at an inferior end 658. The first attachment portion 652includes a first opening 660 which is oriented in a transverse directionand further includes a relief 662 positioned superior to a midline ofthe first opening 660. The second attachment portion 654 includes asecond opening 664 which is oriented in a transverse direction andfurther includes a relief 666 positioned inferior to a midline of thesecond opening 664. The relief 660 is connected to the first opening 660and the relief 666 is connected to the second opening 664.

Referring now to FIG. 39, the dynamic spinal fixation system 670includes first attachment portion 672, second attachment portion 674,and intermediate portion 676 which connects first attachment portion 672and second attachment portion 674. The first attachment portion 672 isat a superior end 678 of the system 670 and the second attachmentportion 674 is at an inferior end 680. The first attachment portion 672includes a first opening 682 which is oriented in a transverse directionand further includes a relief 684 positioned inferior to a midline ofthe first opening 682. The second attachment portion 674 includes asecond opening 686 which is oriented in a transverse direction andfurther includes a relief 688 positioned superior to a midline of thesecond opening 686. The relief 684 is connected to the first opening 682and the relief 688 is connected to the second opening 686.

In the embodiments depicted in FIGS. 34-45, at least one of theattachment portions contains at least one relief allowing a bonefastener head to pass through the dynamic spinal fixation systems.Alternatively, more than one attachment portion may have a reliefallowing a bone fastener to pass through the dynamic spinal fixationsystems. Further, all the attachment portions could have reliefsallowing bone fasteners to pass through the dynamic spinal fixationsystems. The intermediate portions of FIGS. 34-45 may be reinforced withan absorbable biomaterial that is resorbed over time and as thebiomaterial is absorbed, the stiffness of the dynamic spinal fixationsystems changes. Although the systems illustrated in FIGS. 34-45 onlyshow one level systems, multiple level systems are also contemplated andthese multiple level systems include at least one attachment portionwith a relief. In addition, the length of each system shown in FIGS.34-45 may be adjustable to accommodate the spacing between thealready-placed bone fasteners. The systems may also be compressed orextended to allow the already-placed bone fasteners to pass through thereliefs in the attachment portions.

Referring now to FIG. 40, a dynamic spinal fixation system 700 is shown.The system 700 includes a first attachment portion 702, secondattachment portion 704, and intermediate portion 706 which connectsfirst attachment portion 702 and second attachment portion 704. Thefirst attachment portion 702 and second attachment portion 704 are ofthe type described above with reference to first attachment portion 702and second attachment portion 704 of FIGS. 34-35. The intermediateportion 706 or spring-like elastic section has a non-uniformcross-sectional geometry which facilitates the desired stiffnesses indifferent bending directions. For example, the thickened lateralcross-sectional geometry 708 selectively increases torsional stiffnesswithout significantly increasing flexion/extension stiffness.

As best seen in FIGS. 41-43, another dynamic spinal fixation system 720is shown. The system 720 includes a first attachment portion 722, secondattachment portion 724, and intermediate portion 726 which connectsfirst attachment portion 722 and second attachment portion 724. Thefirst attachment portion 722 includes a first opening 728 that isoriented in a transverse direction and further includes a relief 732.The second attachment portion 724 includes a second opening 730 that isoriented in a transverse direction and further includes a relief 734.The reliefs 732, 734 are centered in the first and second openings 728,730, respectively. The intermediate portion 726 includes at least oneelastic mechanism with a plurality of straight portions 736 and aplurality of curved portions 738 and at least one support strut 740. Thesupport struts 740 may be lateral to the midline and at differentdistances from the midline based on the desired rigidity of theintermediate portion 726. The support struts 740 are generally parallelto the curved portions 738 and are located between the straight portions736. In the depicted embodiment there are four support struts 740.

Referring now to FIG. 41, an opening 742 is created between the curvedportions 738 and the support struts 740. In FIG. 42, an opening 744 iscreated between the curved portions 738 and the support struts 740. Theopening 744 is larger than the opening 742 because the support struts740 are closer to the midline in FIG. 42 than in FIG. 41. Referring nowto FIG. 43, an opening 746 is created between the curved portions 738and the support struts 740. Opening 746 is larger than openings 742 and744 because the support struts 740 are closer to the midline in FIG. 43than in either FIG. 41 or 42. The support struts 740 may provide variouslevels of rigidity by reinforcing the intermediate portion 726. Theamount of rigidity which intermediate portion 726 has will be based onthe distance the support strut 740 is from the midline or the size ofthe openings 742, 744, and 746. For example, the system 720 of FIG. 43will be more rigid than the system of FIG. 42 and both will be morerigid than the system of FIG. 41 because strut 740 in FIG. 43 is closestto the midline creating the largest opening 746 and strut 740 in FIG. 41is farthest from the midline creating the smallest opening 742. Therigidity may be enhanced as the support struts 740 are moved closer tothe midline, in particular in bending and torsion, while still allowingthe system 720 to deform elastically.

FIGS. 44 and 45 illustrate another embodiment of a dynamic spinalfixation system 690. The system 690 includes a first attachment portion602, a second attachment portion 604, and an intermediate portion 106.The first attachment portion 602 and second attachment portion 604 areof the type described above with reference to FIGS. 36 and 37. Theintermediate portion 106 is of the type described above with referenceto FIG. 7 wherein the intermediate portion 106 includes at least onesupport strut 122.

Referring now to FIGS. 46-48, another embodiment of a dynamic spinalfixation system 750 is shown with a method of inserting the system 750onto two vertebrae. The system 750 includes a first open attachmentportion or platform section 752, a second open attachment portion orplatform section 754, and an intermediate portion 756. The intermediateportion 756 may be reinforced with an absorbable biomaterial that isresorbed over time and as the biomaterial is absorbed, the stiffness ofthe dynamic spinal fixation systems changes. The first open attachmentportion 752 and second open attachment portion 754 are open on at leastone side. The first open attachment portion 752 includes a base 758, anarm 760, and a hinge mechanism 762 which connects the arm 760 to thebase 758 and allows for the arm 760 to open and close. The second openattachment portion 754 includes a base 764, an arm 766, and a hingemechanism 768 which connects the arm 766 to the base 764 and allows forthe arm 760 to open and close. The system 750 may be secured to a firstvertebra 770 and a second vertebra 772 by first inserting bone fasteners774 into the first vertebra 770 and inserting bone fasteners 776 intothe second vertebra 772. The bone fasteners 774, 776 are screws in thedepicted embodiment, but may also be nails, staples, wires, pins, andthe like. Next the arms 760 and 766 are placed in an open position andbase 758 is aligned with fasteners 774 and base 764 is aligned withfasteners 776. The system 750 may then be slid laterally between thealready inserted bone fasteners 774 and 776 and the first and secondvertebrae 770 and 772, respectively. The arms 760 and 766 may then belowered to close the first attachment portion 752 and the secondattachment portion 754 using the hinge mechanisms 762, 768 or similarmechanism. When the arms 760 and 766 have been lowered, the bonefasteners 774 and 776 are captured within the first open attachmentportion 752 and second open attachment portion 754, respectively. Bonefasteners 774 and 776 may then be tightened to secure the system 750 tothe first and second vertebrae 770 and 772, respectively.

Another dynamic spinal fixation system 800 is shown in FIG. 49. Thesystem 800 includes two first attachment portions 802, two secondattachment portions 804, and at least one brace 806. The firstattachment portions 802 include first attachment sections 808 and firststrut portions 810. The second attachment portions 804 include secondattachment sections 812 and second strut portions 814. The first strutportions 810 of the two first attachment portions 802 are connectedvertically to the second strut portions 814 of the two second attachmentportions 804. The strut portions 810 and 814 include a mechanism thathas an adjustable length. The attachment portions 802 and 804 have agenerally u-shaped geometry that are open on the outside allowing theattachment portions 802 and 804 to be slid between bone fastener headsand the vertebrae. The attachment portions 802 are slid in a superiordirection between vertebra 816 and fastener heads 820 to capture thesystem 800. The attachment portions 804 are slid in an inferiordirection between vertebra 818 and fastener heads 822 to capture thesystem 800. Once attachment portions 802 and 804 are slid into place,although not shown, a hinged enclosure, like the arms 760 and 766 ofFIGS. 46-48, may capture the bone fastener heads 820 and 822.

Illustrated in FIG. 50 is another dynamic spinal fixation system 830.The system 830 includes a first attachment portion 832, a secondattachment portion 834, and two bone fasteners 836. The first attachmentportion 832 includes a first attachment section 834 and a first strutportion 836. The second attachment portion 838 includes a secondattachment section 840 and a second strut portion 842. The attachmentportions 832 and 834 have a generally U-shaped geometry that is open onthe outside allowing the attachment portions 832 and 834 to be slidbetween bone fastener heads 844 and the vertebrae. The attachmentportion 832 is slid in a superior direction and the attachment portion834 is slid in an inferior direction between the vertebrae and bonefastener heads 844 to capture system 830. The strut portions 840 and 842include a mechanism that has an adjustable length and the first strutportion 836 includes a plurality of teeth 846 to facilitate engagementof an adjustable mechanism. The systems 750, 800, and 830 of FIGS. 46-50may be reinforced with an absorbable biomaterial that is resorbed overtime and as the biomaterial is absorbed, the stiffness of the dynamicspinal fixation systems changes.

Referring now to FIGS. 51-55, a surgical method for implanting a dynamicspinal fixation system is depicted and will now be described. The methodutilizes some of the devices, features, aspects, components and the likedescribed above, and therefore reference will be made to the abovedescribed embodiments, such as the illustrated embodiments presented inthe figures and discussed above. However, such references are made forexemplary purposes only and are not intended to limit the surgicalmethod beyond the specifically recited steps. Further, the surgicalmethod may be discussed under the umbrella of particular vertebrae, butsuch an application is not intended to be limiting and the methoddescribed herein may be used or conducted with vertebrae notspecifically discussed herein without departing from the spirit andscope of the surgical method.

Assuming the patient has a spinal injury, disease, or trauma, ananterior spinal surgery, such as an anterior cervical discectomy andfusion (“ACDF”), may be performed to correct the damaged spine using thesystems 550 or 600. The methods disclosed each include placing the bonefasteners first and the systems 550 or 600 second. The fasteners mayalso be used to distract or compress the spine prior to placement of thesystems 550 or 600 over the fasteners.

As depicted in FIG. 56, the method 900 consists of the following steps.First, in order to correct a damaged spine an anterior or lateralportion of the spine is exposed by a surgeon, the vertebral level isdetermined, and the midline position is identified 902. The bonefasteners, screws in the depicted embodiments, are then applied at thesuperior vertebra and the inferior most vertebrae leaving a gap betweenthe screws and the vertebrae 904. A discectomy or corpectomy is thenperformed by inserting a distractor into the screws for distraction andonce decompression is complete a graft, implant, or interbody spacer isplaced into the disc space and then the distraction apparatus is removed906. Next a system of a desired length is chosen to correspond to thedistance between the screws and if compression or distraction isdesired, a smaller or larger system is selected. Alternatively, thelength of the system may be adjusted by compressing or distracting thesystem prior to placing the reliefs over the screw heads and translatingthe system to capture the attachment portions between the screw headsand vertebrae 908. The screws are then tightened to secure theattachment portions between the screw heads and vertebrae withadditional screws being inserted through the openings 910 if necessary.Finally, the patient's incision is closed 912.

When a dynamic spinal fixation system is chosen for step 908 theinter-screw distance must first be determined. Then a surgeon mustdecide whether it is desirable to apply compression or extension to thegraft. If the surgeon wishes to apply compression to the graft then ashorter system 550 or 600 is utilized or the system 550 or 600 may bestretched or expanded prior to placing it over the screws.Alternatively, if the surgeon wants to apply distraction to the graftthen a longer system 550 or 600 is utilized or the system 550 or 600 maybe compressed prior to placing it over the screws.

As illustrated in FIGS. 51-52, in step 904, a first fastener 920 may beapplied to the superior vertebra 924 approximately 2 to 3 millimeters(“mm”) off the midline to the right or left side. A second fastener 922is then applied to the inferior most vertebrae 926 just off the midline,approximately 2 to 3 mm, and on the same side as the first fastener 920.The first vertebra may be adjacent the second vertebra. Alternatively,the first vertebra may be separated from the second vertebra, forexample, the first vertebra may be the C4 and the second vertebra may bethe C6 in a two level procedure. In the depicted embodiment, the firstand second fasteners 920, 922 are applied to the left side of themidline of the vertebrae 924, 926. The reliefs 564, 568 of dynamicspinal fixation system 550 are aligned with the already placed fasteners920, 922. The system 550 is then slid in line with the midline of thespine and the fasteners 920, 922 move into the left lateral sides of theopenings 562, 566, respectively. After the system 550 is positioned,additional fasteners may be applied on the right lateral sides of theopenings 562, 566. The fasteners may then be locked to the system 550 bya locking mechanism, such as an expansion screw or an interference typeplate or screw. The first and second fasteners 920, 922 may also beapplied to the right side of the midline of the vertebrae 924, 926 andthen the fasteners 920, 922 would be slid to the right lateral sides ofthe openings 562, 566, respectively.

As illustrated in FIGS. 53-55, in step 904, a first fastener 920 may beapplied to the superior vertebra 924 approximately 2 to 3 mm off themidline to the right or left side. A second fastener 922 is then appliedto the inferior most vertebrae 926 just off the midline, approximately 2to 3 mm, and on the side opposite the first fastener 920. The firstvertebra may be adjacent the second vertebra. Alternatively, the firstvertebra may be separated from the second vertebra, for example, thefirst vertebra may be the C4 and the second vertebra may be the C6 in atwo level procedure. In the depicted embodiment the first fastener 920is applied to the left side of the midline of the vertebra 924 and thesecond fastener 922 is applied to the right side of the midline of thevertebra 926. Alternatively, the first fastener 920 may be applied tothe right side of the midline of the vertebra 924 and the secondfastener 922 may be applied to the left side of the midline of thevertebra 926. In still another alternative embodiment, the first andsecond fasteners 920 and 922 may be aligned parallel in the vertebrae924 and 926, respectively.

Once the fasteners 920, 922 are inserted into the vertebrae 924, 926, adynamic spinal fixation system 600 is aligned at an angle with the firstfastener 920 and the second fastener 922 so that the previously placedfasteners 920 and 922 are accommodated at the reliefs 614 and 618 in thefirst attachment portion 602 and the second attachment portion 604,respectively. The openings 612 and 616 are curved and concave withrespect to the center of the system 600. The curved and concave openings612 and 616 allow the system 600 to be rotated once the system 600 isplaced over at least one of the already placed fasteners 920 and/or 922.The system 600 is then rotated in line with the midline of the spine andthe fasteners 920 and 922 move into the openings 612 and 616, as bestillustrated in FIG. 52. As the system 600 is rotated the radius ofcurvature of the openings 612 and 616 allows for compression ordistraction of the intermediate portion 606 when the system 600 isrotated under the fasteners 920 and 922.

In an alternative embodiment, the first and second fasteners 920, 922may be applied to the vertebrae 924, 926 parallel to each other. Thesystem 600 is aligned parallel with the fasteners 920, 922 and thereliefs 614 and 618 are aligned with the fasteners 920, 922. Then system600 is slid into position moving the fasteners 920, 922 into theopenings 612, 616.

Once the system 600 is rotated to the desired position along the spine,the first attachment portion 602 and second attachment portion 604 arecaptured between the heads of the fasteners 920 and 922 and the superiorvertebra 924 and inferior vertebrae 926. A third fastener 928 mayoptionally be inserted into the opening 612 and a fourth fastener 930may also optionally be inserted into the opening 616 to further securethe system 600 to the first and second vertebrae 924 and 926,respectively. In alternative embodiments, the openings 612 and 616 mayalso be convex with respect to the center of the system 600 and therebyallow for compression of the intermediate portion 606 when the system600 is slid laterally under at least one fastener. Although the methodhas been described with inserting the fasteners in a given sequence, itis understood by one skilled in the art that the fasteners may beinserted into the spine in any sequence and that the dynamic spinalfixation systems may be slide or rotated in either direction.

While the above detailed description of the invention is in the contextof the cervical spine, it is understood by one skilled in the art thatthe same design is scalable for use in the lumbar spine for anteriorlumbar interbody fusion (“ALIF”) or dynamic stabilization of thecervical and lumbar spine. Further while the preferred and alternativeembodiments are comprised of a metallic material, it is understood thatthe same design is achievable through use of an elastic, hyperelastic,or deformable polymer, ceramic, or composite.

The invention has been described with reference to the preferredembodiments. It will be understood that the architectural andoperational embodiments described herein are exemplary of a plurality ofpossible arrangements to provide the same general features,characteristics, and general system operation. Modifications andalterations will occur to others upon a reading and understanding of thepreceding detailed description. It is intended that the invention beconstrued as including all such modifications and alterations.

What is claimed is:
 1. A fixation system, comprising: a member with asuperior end and an inferior end comprising: a first attachment portionat the superior end, wherein the first attachment portion includes afirst bone fastener opening; a second attachment portion at the inferiorend, wherein the second attachment portion includes a second bonefastener opening; and an intermediate portion connecting the firstattachment portion and the second attachment portion, wherein theintermediate portion comprises: a plurality of intermediate attachmentportions, each intermediate attachment portion with an opening; aplurality of first elastic mechanisms, wherein a first one of theplurality of first elastic mechanisms connects the first attachmentportion and a first one of the plurality of intermediate attachmentportions; and a second elastic mechanism connecting one of the pluralityof intermediate attachment portions and the second attachment portion.2. The fixation system of claim 1, wherein the member has a width and adepth, the width is at least two times the depth and the width extendsalong the straight sections between the curved sections and the depthextends between a front surface and a back surface of the member.
 3. Thefixation system of claim 1, wherein the member is asymmetrical acrossthe sagittal plane, the member is asymmetrical across the transverseplane, and the member is asymmetrical across the coronal plane.
 4. Thefixation system of claim 1, wherein the intermediate portion is anelastic mechanism and wherein the elastic mechanism includes a pluralityof curved sections and straight sections, wherein the curved sectionsare connected to the straight sections.
 5. The fixation system of claim1, wherein the straight sections are transverse to the sagittal plane.6. The fixation system of claim 1, wherein the cross-section of theelastic mechanism in the sagittal plane is selected from polygonal inthe sagittal plane and oblong in the sagittal plane.
 7. The fixationsystem of claim 1, further comprising: a relief in at least one of thefirst bone fastener opening and the second bone fastener opening.
 8. Thefixation system of claim 7, wherein the first bone fastener opening hasa first relief and the position of the first relief is selected fromcentered in the first bone fastener opening, superiorly in the firstbone fastener opening, and inferiorly in the first bone fastener openingand wherein the second bone fastener opening has a second relief and theposition of the second relief is selected from centered in the secondbone fastener opening, superiorly in the second bone fastener opening,and inferiorly in the second bone fastener opening.
 9. The fixationsystem of claim 8, wherein the first relief of the first attachmentportion is sized to receive a first bone fastener and the second reliefof the second attachment portion is sized to receive a second bonefastener.
 10. The fixation system of claim 1, wherein the first bonefastener opening and the second bone fastener opening are curved in thecoronal plane along a midline of the member.
 11. The fixation system ofclaim 1, wherein the member is curved in the sagittal plane tocorrespond to the shape of a patient's spine and in the transverse planeto correspond to the shape of the patient's vertebrae.
 12. The fixationsystem of claim 1, wherein the intermediate portion includes at leastone support strut.
 13. The fixation system of claim 12, wherein the atleast one support strut is selected from the group consisting of:positioned from lateral to a midline of the member; positioned alignedalong the midline of the member; and positioned adjacent to at least oneof the plurality of curved sections forming an opening between the atleast one support strut and at least one of the plurality of curvedsections.
 14. The fixation system of claim 1, wherein the member furthercomprises: at least one stop member positioned between two adjacentsections of the elastic mechanism.
 15. The fixation system of claim 14,wherein the at least one stop member is positioned between two adjacentstraight sections of the elastic mechanism.
 16. The fixation system ofclaim 15, wherein the at least one stop member is selected from thegroup consisting of: a first portion to stop movement of the elasticmechanism along a superior-inferior axis; and a first portion attachedadjacent to a second portion and wherein the first portion mates withthe second portion to inhibit movement of the elastic mechanism along asuperior-inferior axis.
 17. The fixation system of claim 1, furthercomprising: an interbody fusion cage device coupled to the intermediateportion.